This invention relates to a prepayment metering system for services such as electricity, gas and water.
It is usual for meters to be read by an official from the supply company from time to time to enable a charge to be computed, or for a consumer to put coins or tokens into a meter as prepayment for units of electricity, gas or water, the coins or tokens being collected at intervals by an inspector. The requirement for an inspector to call at the consumer premises from time to time is an onerous one, particularly in cases where a consumer is rarely at home. Ways of avoiding such visits have therefore been considered and solutions have been proposed such as generating at a terminal station a signal identifying a particular meter and sending this signal over electricity supply lines, the meter including a recognition circuit which, on receipt of its identification signal, triggers a meter reading device which then sends a signal representing the reading back along the supply lines to the terminal station. However, such systems are expensive in the equipment required at the consumer premises.